Valorization of Coal Fly Ash as a Stabilizer for the Development of Ni/CaO-Based Bifunctional Material

Sorption-enhanced glycerol steam reforming (SEGSR) is considered as one of the promising processes for H 2 production by combining glycerol steam reforming with simultaneous CO 2 capture in a single-unit operation. The key challenge for a successful SEGSR process is the selection of suitable high-temperature CO 2 sorbents with high resistance to sintering. In the present work, an attempt was made to modify a CaO-based sorbent by adding different types of coal fly ash (FA1–FA12) to develop highly effective and economical CaO-based sorbents suitable for CO 2 removal at high temperatures. Among the synthesized sorbents, the 90%CaO–FA5 sorbent offered the most stable CO 2 capture activity over 20 cycles, with a CO 2 capture capacity of 0.58 g CO 2 /g sorbent at the 1st cycle and 0.45 g CO 2 /g sorbent at the 20th cycle. This can be attributed to the relatively high amounts of SiO 2 and mullite (inert materials) in FA5 compared with those of the other FA-containing samples. The presence of these inert materials helps enhancing the sorbent stability by hindering their aggregation and sintering. This sorbent was then selected to synthesize a bifunctional catalyst–sorbent material for H 2 production via SEGSR. The 15%Ni–CaO–FA5 bifunctional material exhibited a stable H 2 purity of ∼97% and a H 2 yield of ∼90% for 30 min (prebreakthrough) of the SEGSR reaction. These results highlight the high potential of FA5 as a low-cost stabilizer for improving the stability of CaO-based sorbents.